The atomic layer deposition method, in which gases of elements constituting a thin film to be formed are alternately supplied onto a substrate to form a thin film in units of atomic layers on the substrate, is known as a technique for uniformly forming a thin film. Compared with a common CVD (Chemical Vapor Deposition) method, the atomic layer deposition method excels in step covering property and film thickness controllability.
Repeating the formation of a thin film by the atomic layer deposition method will lead to adhesion of the thin film even on an inner surface of a film forming chamber. As the thickness of the thin film adhered to the inner surface of the film forming chamber increases, the deposited thin film will be peeled off and part of the thin film becomes particles, causing deterioration of the quality of the thin film formed on the substrate. For that reason, it is preferable to remove the thin film deposited on the inner surface of the film forming chamber at regular intervals.
Patent Literature 1 proposes a processing method and apparatus in which an anti-adhesion plate is used and besides deposits deposited on the inner wall of a chamber are covered with an amorphous film in a vapor-phase growing apparatus for CVD film forming, sputter film forming, and the like. Although it is possible to reduce the frequency of cleaning by such means in a conventional vapor-phase growing apparatus, when the thickness of the deposits deposited on the inner wall of the chamber and the amorphous film covering the deposits becomes not less than a predetermined thickness, it is necessary to perform cleaning by using a wet etching method. However, in the wet etching method, since the film forming chamber is opened up, the time and effort for the opening work increases as the size of the film forming chamber increases, and therefore, when a gas etching method can be used, it is preferable to use the gas etching method. To perform etching by the gas etching method, while it is necessary to heat a portion of the inner wall surface of the film forming chamber, onto which a thin film has adhered, to a temperature not less than a predetermined temperature, a portion apart from the heater may not reach a necessary heating temperature, making it difficult to perform gas etching. For that reason, if a certain amount of thin film has adhered to a location where it is difficult to perform gas etching, it becomes necessary to open up the film forming chamber and perform wet etching.
There is proposed a technique for inserting an anti-adhesion plate in a film forming chamber for the purpose of increasing the interval of wet etching, and further suppressing film adhesion to the film forming chamber body (Patent Literature 2). In a conventional scheme, the anti-adhesion plate is divided to be placed in the film forming chamber. Dividing the anti-adhesion plate makes the handling thereof easy, and further, in the case of an apparatus for heating to higher temperatures, it becomes possible to absorb thermal expansion of the anti-adhesion plate by providing space in gaps between divided anti-adhesion plates.
However, in an apparatus for atomic layer deposition, a raw material gas and a reaction gas will readily infiltrate into fine gaps, forming films. Gases that have filtrated into such fine gaps turn into film and powder, thus causing particles. Therefore, in an apparatus for atomic layer deposition, it is preferable to suppress the dividing of the anti-adhesion plate as much as possible.
To suppress film adhesion in a case in which the dividing of anti-adhesion plate is needed, it is possible to employ a method of supplying inert gas as shown, for example, in Patent Literature 3.
Moreover, in an atomic layer deposition without use of plasma, it is possible to protect an upper part of the substrate by employing the anti-adhesion plate shown in Patent Literature 4. On the other hand, in a parallel-plate type plasma apparatus, in which an electrode for applying high-frequency voltage to an upper section of the substrate is placed, an insulator is used for supporting the electrode to which high-frequency voltage is applied. For this insulator, mainly, resins such as Teflon (registered trademark), and ceramics are used.